This invention relates to a fuel injection valve for an internal combustion engine and, more particularly, to a direct injecting fuel injection valve for an internal combustion engine of the type mounted to an engine cylinder for directly injecting the fuel into the cylinder.
The direct injection type fuel injection valve, which is to be mounted to the internal combustion engine cylinder for directly injecting the fuel into the combustion chamber, is required to endure severe environmental conditions peculiar to the direct fuel injection. The performances required for enduring these environmental conditions include mechanical strength against the heat and the vibration of the cylinder, the high pressure of the combustion gas within the combustion chamber and mechanical strength against the elevated temperature as well as the sealing ability for the prevention of the leakage of the fuel and the combustion gas, the electric and magnetic properties and the corrosion resistivity against the chemical components and the residual components within the fuel and the combustion gas.
The typical structure of the direct injection fuel injection valve is such that a hollow injection valve main body in which a needle valve is accommodated is connected to a housing by the press-fit or the like and a solenoid is disposed within the housing for actuating the needle valve. The mounting of the fuel injection valve to the cylinder is usually achieved by inserting the injection valve main body into a bore provided in the cylinder head and by urging and attaching a housing of the injection valve against the cylinder head by means of the fuel supply pipe.
The direct injection fuel injection valve disclosed in Japanese Utility Model Laid-Open No. 7-30368 is designed for preventing the shrinkage of the axial length of the housing due to the mounting load acting on the fuel injection valve from influencing the lift stroke of the needle valve of the injection valve, and the fuel injection valve is inserted at the tip of the injection valve main body until it abuts against the bottom of the injection valve insertion hole provided in the cylinder head and axially urged against and fixed to the cylinder head. A gasket having a recess for receiving the tip of the injection valve main body therein is press-fit on the tip of the injection valve main body so that a clearance is defined between the bottom surface of the recess of the gasket and the tip of injection valve main body.
In this direct injecting fuel injection valve, the mounting load in the axial direction for mounting the fuel injection nozzle to the cylinder only causes the clearance between the gasket and the injection valve which are held together by the press-fit friction therebetween to decrease and does not cause the length dimension of the housing to be reduced to decrease the lift amount of the needle valve.
However, in this type of fuel injection valve in which the housing and the injection valve main body are connected together, the connection portion is inevitably subjected to a massive pressing force irrespective of the means of connection which may be press-fit, weld or caulking, often causing the strength of the connection portion to be insufficient, resulting in a difficulty in maintaining the precise lift stroke of the valve. This connection portion in the housing must at the same time be durable against the influences of the thermal expansion, the thermal displacement, the thermal shocks or the like due to the high temperature of the internal combustion engine. The housing is also required to have the sealing ability against the fuel and the combustion gas as well as to provide a magnetic circuit for the solenoid and, furthermore, the minimum dimensions are required for the light-weight and the compactness of the fuel injection valve.